Fillers and methods for displacing tissues to improve radiological outcomes

ABSTRACT

Certain embodiments include a method of improvising radiological outcomes by introducing a filler to between a first tissue location and a second tissue location to increase a distance between the first tissue location and the second tissue location, and administering a dose of radioactivity to at least the first tissue location or the second tissue location. Collagen and hyaluronic acid are examples of fillers. Certain embodiments include a medical device having a biocompatible, biodegradable filler material, wherein the device comprises at least a portion that has a shape that substantially conforms to Denovillier&#39;s space between the rectum and prostate. Certain embodiments include a kit, the kit comprising a filler and instructions for placing the filler between a first tissue location and a second tissue location to increase a distance between the first tissue location and the second tissue location.

RELATED APPLICATIONS

This application claims priority to U.S. provisional patents 60/427,662filed Nov. 19, 2002, 60/391,027 filed Jun. 24, 2002, and 60/444,143,filed Jan. 31, 2003, which are hereby incorporated herein by reference.

BACKGROUND

Over 198,100 men will be diagnosed with prostate cancer each year.Typically, forty percent will choose interstitial implant therapy,one-third of the men will choose surgery, and one third will chooseexternal beam radiotherapy.

Typical treatments for prostate cancer include surgical removal of theprostate (prostatectomy), freezing the prostate (cryosurgery), hormonaltherapy, prostate seed implant therapy, or prostate conformal radiation.

The treatment providing the best outcome is still debatable. However,the side effects of treating prostate cancer have become less toxic andless profound with implant therapy and 3D conformal radiotherapy.Advancements in treatment positioning and target localization havesignificantly improved outcomes and diminished the side effects.

Since the conception of 3D conformal radiotherapy, physicians have paidattention to the delivered dose to the target and surrounding tissues.Investigators have been able to correlate side effects to the amount oftissue receiving a certain radiation dose. This term has been coined:dose volume histogram. For conformal radiotherapy it is conventionallypreferred that the rectum receive less than 40% of the prescribedtreatment dose in hopes of minimizing the radiation induced sideeffects.

Time, distance, and shielding affect the dose that is delivered. Theless time an area is exposed to radiation, the less dose delivered. Thegreater the distance from the radiation, the less dose delivered.Finally, more shielding will also decrease the delivered dose.

SUMMARY OF CERTAIN EMBODIMENTS OF THE INVENTION

It would be desirable to provide a protocol to decrease the radiationdose to the rectum during radiotherapy for prostate cancer. It is alsodesirable to decrease radiation treatment-induced side effects onsensitive organs resulting from other therapies and applicationsdirected to a target organ. Certain embodiments of the present inventionaddress these issues.

Certain embodiments are a medical device, the device having abiocompatible, biodegradable filler material, wherein the devicecomprises at least a portion that has a shape that substantiallyconforms to the space between two tissue locations, e.g., Denovillier'sspace.

Certain embodiments are a method comprising introducing a filler tobetween a first tissue location and a second tissue location to increasea distance between the first tissue location and the second tissuelocation. Further, there maybe a step of administering a dose ofradioactivity to at least the first tissue location or the second tissuelocation.

Certain embodiments are directed to kits having a filler, instructionsfor placing the filler between tissues in conjunction with a treatment,e.g., radiation or cryogenics, and an optional delivery device.

Certain embodiments may have a filler material that comprises anextracellular matrix molecule. Certain embodiments may have a fillermaterial that is biodegradable in vivo in less than approximately 90days. Certain embodiments may have at least one therapeutic agent.Certain embodiments may have a buffering agent. Certain embodiments mayhave a total volume or a volume of filler in the range of about 10 toabout 50 cubic centimeters, wither before or after the device or filleris introduced into the patient. An expandable device may be used forfiller, e.g., a balloon or sponge. Or the filler material may comprise asynthetic polymer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts the male prostate, rectum and Denovillier's space betweenthe prostate and rectum.

FIG. 2 depicts the insertion of a needle into the space between theprostate and rectum for injecting collagen therein.

FIG. 3 depicts the injected collagen within Denovillier's space betweenthe prostate and the rectum.

FIG. 4 depicts a computer tomography (CT) image of a patient's pelvisshowing a collagen filler placed between the prostate and rectum of thepatient.

DETAILED DESCRIPTION

Certain embodiments of the invention comprise placing a filler betweenthe radiation target tissue and other tissues. The filler increases thedistance between the target tissue and other tissues so that the othertissues receive less radiation. In some embodiments, the filler is adegradable material that is installed once prior to the course ofradiation treatment and does not require subsequent manipulation,repositioning, or removal. Some fillers maintain their naturalproperties during and after exposure to radiation and remain in the samelocation until after a treatment course has concluded. Other embodimentsinclude fillers made with inflatable devices that are introduced betweenthe target tissue and other tissue; such inflatable devices may be leftin the patient during the course of radiation treatment or removed andreintroduced periodically during the course of radiation treatment.Certain of the embodiments set forth herein address various advantagesthat are described in the context of the evolution of the prostatetreatment procedures.

The modern era has witnessed the evolution of radical prostatectomy,external beam radiotherapy and interstitial permanent seed Brachytherapyto a point where the results are nearly equivalent. Although someauthors may debate that their technique has achieved superior results,by and large the results have been too close to claim that one modalityis definitely superior to the other. If this is so, then the decisionfor therapy must consider treatment related side effects.

External beam radiotherapy may cause radiation-induced side effects forprostate cancer. Modern radiation treatment using 3D conformal therapyand most recently, intensity modulated radiotherapy (IMRT) hassignificantly reduced treatment related side effects. However, suchtreatments continue to require special consideration for the rectum,which is particularly sensitive to radiation. Care is taken to ensurethat the rectum receives a dose that is well tolerated and diminishesthe probability of treatment related side effects. Others have evaluatedthe effectiveness of daily insertion of rectal catheters and dailyadministration of rectal radioprotectants, and have achieved only modestsuccess.

Some investigators are attempting to decrease the dose to the anteriorrectal wall and thereby decrease the potential for radiation inducedside effects on the rectum. One such technique is to insert aninflatable Foley catheter into the rectum on a daily basis duringradiation treatments. The premise is that more of the rectum isdisplaced away from the prostate than the small portion of rectum thatis pushed toward the prostate. Therefore a smaller amount of rectum isreceiving radiation and consequently the side effects from radiationshould be diminished.

However, certain embodiments set forth herein have advantages that mayinclude the reduction of radiation side effects, improved costeffectiveness, the need to perform only one or a few procedures toachieve a reduction in radiation, no requirement for removal of thetreatment after its administration, and ease of use, e.g., by a patient,nurse, or technician.

Example 2 includes a study that shows that injection of human collageninto Denovillier's space can change the radiation dose that the rectumreceives when the prostate is exposed to radiation. “Denovillier'sspace” is a region located between the rectum and prostate. The collagenwas well tolerated and withstood the radiation treatments. The collagendegraded in less than about sixty days and required no procedures afterits initial introduction into the patients. The study was a trialinvolving 10 men who received human collagen injections intoDenovillier's space to displace the rectum away from the prostate priorto proceeding with their radiotherapy. The injections were welltolerated and could readily be performed on an outpatient basis. Theradiation dose to the rectum was diminished by over approximately 50%when 20 cc's of human collagen was injected into Denovillier's space.Moreover, men who have received human collagen injections appeared tohave minimal rectal side effects associated from their radiotherapy andhad no appreciable changes associated due to the collagen.

This procedure was well-tolerated by the patients. Indeed, others havereported that human collagen has been used in various body areas and iswell tolerated. For example, it has been injected into a the perineum inhopes of improving urinary incontinence. And human collagen has receivedUnited States Food and Drug Administration approval to be used inbrachytherapy procedures as a spacer. Further, it is known that normalsaline may be injected into the potential space between the rectum andprostate prior to proceeding with cryotherapy to minimize the freezingeffect on the rectum, so displacement of the tissues aroundDenovillier's space is known to be well-tolerated.

The successful use of collagen as a filler shows that other materialsmay also be used. Other materials may include natural or syntheticmaterials, e.g., proteins, extracellular matrix molecules, fibrin,proteins, hyaluronic acid, albumin, bulking agents, and polyethyleneglycol-based materials. A synthetic material is a material that is notfound in nature.

Certain embodiments provide a method of displacing a tissue to protectthe tissue against the effects of a treatment involving radiation orcryotherapy. One embodiment involves using a filler to displace thetissue relative to a tissue that is to receive the treatment. Anotherembodiment involves introducing a filler to displace a first tissue andradiating a second tissue, particularly a second tissue that is close tothe first tissue. In another embodiment, the method comprises the stepsof injecting a filler into a space between tissues; and may furtherinclude irradiating one of the tissues so that the other tissue receivesless radiation than it would have in the absence of the filler.

Certain embodiments also provide methods for treating a tissue of a bodyby radiation. In one embodiment, the method comprises the steps ofinjecting an effective amount of a filler into a space between a firsttissue (e.g., prostate) of a body and a second tissue (e.g., rectum),which can be a critically sensitive organ; and treating the first tissueby radiation whereby the filler within the space reduces passage ofradiation into the second tissue. Tissue is a broad term thatencompasses a portion of a body: for example, a group of cells, a groupof cells and interstitial matter, an organ, a portion of an organ, or ananatomical portion of a body, e.g., a rectum, ovary, prostate, nerve,cartilage, bone, brain, or portion thereof.

Also provided are embodiments for displacing a sensitive body tissuerelative to another body tissue that is the target of a treatmentprotocol, to effectively reduce side effects on/in the sensitive tissueinduced by or resulting from a treatment directed to the target tissue.In one embodiment, the method comprises injecting a filler into a spacebetween the sensitive body tissue (e.g., rectum) and the target bodytissue (e.g., prostate); and conducting a treatment protocol on thetarget body tissue whereby the sensitive body tissue is less affected bythe treatment as a result of the presence of the filler.

Examples of embodiments of the treatment include use with suchapplications as external beam radiotherapy (e.g., 3D conformal orIntensity Modulated Radiotherapy), interstitial prostate brachytherapy(e.g., using permanent or temporary seeds, or using High Dose Rateremote after loading), and cryosurgery. Another embodiment is the use ofthese techniques for brachytherapy radiation treatments for prostatecancer or gynecological cancers. Brachytherapy includes the placement ofa radioactive isotope within or near the tumor, target organ, or othertissue. For example, a brachytherapy technique is placement of permanentI-125 radioactive seeds into the prostate for treatment of prostatecancer. Applications for gynecology include embodiments involvingdisplacing a tissue from another tissue that is to be targeted byradiation.

A filler is a substance that occupies a volume after its introductioninto a body. Examples of fillers include but are not limited topolymers, gels, sols, hydrogels, sponges, bulking agents, and balloons.Filler materials include polysaccharides, alginate, collagen, gelatin,fibrin, fibrinogen, albumin, serum, autologous serum, sutures, andnatural and synthetic polymers. Synthetic polymers include polylactide,polyglycolide, polycaprolactones, poly(alpha.-hydroxy acid), poly(aminoacid), and poly(anhydride). Fillers may be crosslinked or uncrosslinked.Polymers include polyethylene glycol and derivatives thereof, includingcrosslinked polyethylene glycols. Other types of polymers includethermoreversible and thixotropic polymers. Other examples of a fillerinclude self-absorbing suture material held within a suspension (such asprolene sutures).

Fillers may include materials that are formed in situ in the body, e.g.,by combining a first precursor and a second precursor to form amaterial, e.g., a gel or hydrogel. Examples include covalent bonding ofelectrophiles and nucleophiles (e.g., see U.S. Pat. No. 5,874,500) andgelation of polysaccharides (e.g., addition of calcium to alginate).Fillers may include materials derived from the body that receives them,e.g., autologous serum. Donor blood may be used to derive somematerials, e.g., albumin. Combinations of materials are alsocontemplated.

Suitable fillers and materials for fillers may include, for example,those set forth in U.S. Pat. Nos. 6,509,031; 6,413,742; 6,388,047;6,280,772; 6,271,278; 6,268,405; 6,129,761; 6,031,148; 6,110,484;5,932,539; 5,874,500; 5,863,984; 5,865,367; 5,759,583; 5,618,563;5,599,552; 4,970,298; 4,703,108; and 4,193,813, which are herebyincorporated by reference in their entirety herein.

Fillers may be biodegradable, either by hydrolysis, proteolysis, theaction of cells in the body, or a combination thereof. Biodegradationmay be measured by palpitation or other observations to detect thechange in volume of a filler after its introduction into a patient.Biocompatible materials are preferred, especially collagen or hyaluronicacid. A suitable length for biodegradation to occur is between one dayand twelve months after introduction of the filler into the body.Alternatively, fillers may remain in place for other periods, includingfrom one week to three months and two to eight weeks. Also the fillermay be biodegraded in less than about two months after implantation, asis preferable for the case of displacing rectal tissue from the prostategland. The time for biodegradability for a specific use may bedetermined by the time required to complete a course of radiation, whichmay vary for different radiological applications and differentrequirements for administering the full course of radiological therapy.

Fillers may include osmotic agents. For example, agents that increasethe osmotic pressure of the filler may be used in the filler. Oneadvantage of an osmotic agent is that it will cause the filler toincrease its volume after its introduction into the body. For example,albumin, human serum, human plasma, salts, or steroids may be added to,or mixed with, the filler.

Fillers may contain drugs or be used to deliver drugs. For example, asteroid may be introduced into the filler. Drugs may include, forexample, steroids, anti-inflammatory agents, agents to inhibitdegradation of the filler (e.g., protease inhibitors), agents to enhancefiller degradation, antibiotics, hemostatics, and antimycotics.

Fillers may also be reversibly introduced. For example, athermoreversible polymer may be introduced as a liquid-like material andallowed to form a gel in situ. Or a polymer may be introduced that isnon degradable or poorly degradable until it is heated to cause itsdegradation or liquefaction.

A filler may have a first physical state before its introduction intothe body and a second physical state after its introduction into thebody. A change in physical state may include, for example, a change involume, viscosity, water content, swelling, or crosslinking. Anotherembodiment is a filler that exists as at least two precursors beforeintroduction into the body and exists as a crosslinked material formedby the mixing of the two precursors after introduction into the body.

For example, solutions containing collagen or collagen-like precursorsmay be introduced into the body. As the solution warms to the bodytemperature as the pH of the solution becomes adjusted to bodily pH, thefibrils cooperate to form a fibrin gel according to well-known processedof collagen formation. The solution has a low viscosity while stored,e.g., as part of a kit, but has a stronger physical structure after itsself-assembly in situ in the patient.

And for example, solutions of polysaccharides may be introduced into thepatient. Some polysaccharides increase in viscosity when exposed tocertain salts, or in response to a change in pH. Products and processesinvolving, for instance, hyaluronic acid solutions or precursors thatgel after introduction into a patient are known.

Thermoplastic polymers include pharmaceutically compatible polymers thatare bioerodible by cellular action, are biodegradable by action ofnon-living body fluid components, soften when exposed to heat but returnto the original state when cooled and are capable of substantiallydissolving or dispersing in a water-miscible carrier or solvent to forma solution or dispersion. Upon contact with an aqueous fluid and thedissipation of the solvent component, the thermoplastic polymers arecapable of coagulating or solidifying to form a solid or gelatinousmatrix suitable for use as an implant in an animal. The kinds ofthermoplastic polymers suitable for the present composition generallyinclude any having the foregoing characteristics. Examples arepolylactides, polyglycolides, polycaprolactones, polyanhydrides,polyamides, polyurethanes, polyesteramides, polyorthoesters,polydioxanones, polyacetals, polyketals, polycarbonates,polyorthocarbonates, polvphosphazenes, polyhydroxybutyrates,polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates,poly(malic acid), poly(amino acids), poly(methyl vinyl ether),polv(maleic anhydride), chitin, chitosan, and copolymers, terpolymers,or combinations or mixtures therein. Polylactides, polycaprolactones,polyglycolides and copolymers thereof are highly preferred thermoplasticpolymers.

The thermoplastic polymer is combined with a suitable organic solvent toform a solution. The solubility or miscibility of a polymer in aparticular solvent will vary according to factors such as crystallinity,hydrophilicity, capacity for hydrogen-bonding and molecular weight ofthe polymer. Consequently, the molecular weight and the concentration ofthe polymer in the solvent are adjusted to achieve desired miscibility.Highly preferred thermoplastic polymers are those which have a lowdegree of crystallization, a low degree of hydrogen-bonding, lowsolubility in water, and high solubility in organic solvents.

The composition of the invention may as well be a liquid formulation ofa thermosetting oligomeric pre-polymer or copolymer which is capable ofcross-linking or hardening to provide a microporous gelatinous or solidmatrix suitable for use as an implant in an animal, including a human.The thermosetting pre-polymers and resulting cross-linked polymers andcopolymers are biocompatible, and biodegradable and/or bioerodible.

The pre-polymers are preferably low molecular weight polymers oroligomers having end functional groups that are reactive with acryloylchloride to produce acrylic ester-terminated pre-polymers. Acrylicpre-polymers for use in the compositions may be synthesized according toa variety of methods including, but not limited to, reaction of acarboxylic acid, such as acrylic or methacrylic acid, with an alcohol;reaction of a carboxylic acid ester, such as methyl acrylate or methylmethacrylate, with an alcohol by transesterification; and reaction of anisocyanatoalkyl acrylate, such as isocyanatoethyl methacrylate, with analcohol.

The thermosetting prepolymers are also short chain polyol derivatives ofthe thermoplastic polymers described herein. The polyol terminatedderivatives are converted to acrylic ester terminated prepolymers by anysuitable method. Examples are short chain polyol derivatives ofpolylactides, polyglvcolides, polycaprolactones, polyanhydrides,polyamides, polyurethanes of polyesteramides, polyorthoesters,polydioxanones, polyacetals, polyketals, polycarbonates,polyorthocarbonates, polyphosphazenes, polyhygroxybutyrates,polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates,poly(malic acid), poly(amino acids), poly(methyl vinyl ether),poly(maleic anhydride), chitin, chitosan, and copolymers, terpolymers,or combinations or mixtures therein.

A polymer matrix and implant prepared with thermosetting prepolymers iscomposed of poly(DL-lactide-co-caprolactone) (DL-PLC). To prepare theDL-PLC polymer matrix, DL-lactide or L-lactide and .gamma.-caprolactoneare co-polymerized in the presence of a multifunctional polyol initiatorand a curing agent to produce hydroxy-terminated PLC prepolymers. Thispolyol-terminated pre-polymer is then converted to an acrylicester-terminated pre-polymer by any suitable method, as for example, byacylation of the alcohol terminus with acryloyl chloride by means of,for example, a Schotten-Baumann technique (reaction of acyl halide withalcohol).

Optionally, a curing agent, such as a catalyst, may be added to theacrylic pre-polymer mixture to enhance cross-linking of the pre-polymersand the subsequent coagulation or solidification of the resultingpolymer to form a matrix. For example, the acrylic pre-polymer, in anamount of about 5 grams, may be added to a solution of benzoyl peroxide(BP) in about 1 ml of CH₂Cl₂ Optionally, other acrylic monomers may beadded to the acrylic pre-polymer mixture before adding the curing agent.The acrylic pre-polymer mixture may be cured in air at room temperature,or in a preheated vacuum oven.

Preferred catalysts for the preparation of the PLC prepolymers are basicor neutral ester-interchange (transesterification) catalysts, as forexample, metallic esters of carboxylic acids containing up to 18 carbonatoms, formic, acetic, lauric, stearic, and benzoic acid. Preferredcatylists include, for example, stannous octoate and stannous chloride.

A multi-functional polyol chain initiator may be included in thethermosetting polymer compositions to vary the molecular weight andcomposition of the polymer. For example, a bifunctional chain initiatorsuch as ethylene glycol, may be included to produce a bifunctionalpolymer, or a trifunctional initiator, such as trimethylolpropane, maybe used to produce a trifunctional polymer. Further, molecular weight ofthe polymer or co-polymer may be varied according to the concentrationof the chain initiator in the composition. For example, a highconcentration of a bifunctional chain initiator may make available aninitiator molecule for each polymer chain, while a low concentration maycontain one initiator molecule for every two polymer chains.

Following the addition of the curing agent, the pre-polymer polymermixture preferably remains in liquid form for a period of time effectiveto allow administration of the composition to the implant site.Thereafter, the cross-linking reaction preferably continues until asolid or gelatinous polymer matrix is produced. Accordingly, thepre-polymer mixture cures, or solidifies, in situ to form a polymermatrix, which is capable of biodegradation and/or bioabsorption overtime.

A solution that contains a filler gels in response to a change in pH maybe made up at a first pH in solution, but be buffered so that its pHchanges after introduction into a patient. The buffer could berelatively weak compared to physiological buffer saline solutions, or itcould be concentrated. In either case, the buffer would eventuallydiffuse away so that the pH of the filler would be changed.

Similarly, a solution having a filler that changes viscosity,crosslinks, or gels in response to a change in temperature could beintroduced at a first temperature and allowed to transition to bodytemperature in situ in a patient so that it would have a change inproperties.

Fillers may be mixed with salts, buffers, or other pharmaceuticallyacceptable agents, e.g., carriers. Examples of suitable pharmaceuticalcarriers are described, for example, in “Remington's PharmaceuticalSciences” by E. W. Martin. Examples of buffers include phosphates,carbonates, and Tris. Examples of buffer osmolarity are ranges from 10to 3000, from 50 to 600, from 150 to 500, and from 300-350. A bufferingagent may be both a buffer and an osmolarity agent. Fillers may also bemixed with agents to aid their visualization by medical devices, e.g.,by MRI or ultrasound. Fillers may also be mixed with agents that blockradiation.

If the filler contains collagen, the collagen may be natural orsynthetic collagen, and of human origin or non-human origin, such asbovine collagen (e.g., Bovine Type I collagen), for example. Thecollagen can be prepared as a suspension with a pharmaceuticallyacceptable vehicle or carrier (e.g., water) having a pH in thephysiological range. Collagen may be collagen derived from a naturalsource, and may includes collagen isolated from tissue and recombinantlyderived collagen, e.g., collagen produced by genetically engineeredbacteria. Collagen may also be collagen that is not found in nature,e.g., materials intelligently designed to mimic collagen or some of thestructural or functional features of collagen.

Polymeric materials which are capable of forming a hydrogel may beutilized. In one embodiment, the polymer forms a hydrogel within thebody upon contact with a crosslinking agent. A hydrogel is defined as asubstance formed when an organic polymer (natural or synthetic) iscrosslinked via covalent, ionic, or hydrogen bonds to create athree-dimensional open-lattice structure which entraps water moleculesto a gel. Naturally occurring and synthetic hydrogel forming polymers,polymer mixtures and copolymers may be utilized as hydrogel precursors.

Examples of materials which can be used to form a hydrogel includemodified alginates. Alginate is a carbohydrate polymer isolated fromseaweed, which can be crosslinked to form a hydrogel by exposure to adivalent cation such as calcium, as described, for example in WO94/25080. Alginate is ionically crosslinked in the presence of divalentcations, in water, at room temperature, to form a hydrogel matrix.Modified alginate derivatives may be synthesized which have an improvedability to form hydrogels. The use of alginate as the starting materialis advantageous because it is available from more than one source, andis available in good purity and characterization. As used herein, theterm “modified alginates” refers to chemically modified alginates withmodified hydrogel properties. Naturally occurring alginate may bechemical modified to produce alginate polymer derivatives that degrademore quickly. For example, alginate may be chemically cleaved to producesmaller blocks of gellable oligosaccharide blocks and a linear copolymermay be formed with another preselected moiety, e.g. lactic acid or.epsilon.-caprolactone. The resulting polymer includes alginate blockswhich permit ionically catalyzed gelling, and oligoester blocks whichproduce more rapid degradation depending on the synthetic design.Alternatively, alginate polymers may be used, wherein the ratio ofmannuronic acid to guluronic acid does not produce a firm gel, which arederivatized with hydrophobic, water-labile chains, e.g., oligomers of.epsilon.-caprolactone. The hydrophobic interactions induce gelation,until they degrade in the body.

Additionally, polysaccharides which gel by exposure to monovalentcations, including bacterial polysaccharides, such as gellan gum, andplant polysaccharides, such as carrageenans, may be crosslinked to forma hydrogel using methods analogous to those available for thecrosslinking of alginates described above. Polysaccharides which gel inthe presence of monovalent cations form hydrogels upon exposure, forexample, to a solution comprising physiological levels of sodium.Hydrogel precursor solutions also may be osmotically adjusted with anonion, such as mannitol, and then injected to form a gel.

Polysaccharides that are very viscous liquids or are thixotropic, andform a gel over time by the slow evolution of structure, are alsouseful. For example, hyaluronic acid, which forms an injectable gel witha consistency like a hair gel, may be utilized. Modified hyaluronic acidderivatives are particularly useful. As used herein, the term “modifiedhyaluronic acids” refers to chemically modified hyaluronic acids.Modified hyaluronic acids may be designed and synthesized withpreselected chemical modifications to adjust the rate and degree ofcrosslinking and biodegradation. For example, modified hyaluronic acidsmay be designed and synthesized which are esterified with a relativelyhydrophobic group such as propionic acid or benzylic acid to render thepolymer more hydrophobic and gel-forming, or which are grafted withamines to promote electrostatic self-assembly. Modified hyaluronic acidsthus may be synthesized which are injectable, in that they flow understress, but maintain a gel-like structure when not under stress.Hyaluronic acid and hyaluronic derivatives are available from Genzyme,Cambridge Mass. and Fidia, Italy.

Other polymeric hydrogel precursors include polyethyleneoxide-polypropylene glycol block copolymers such as PLURONICS orTETRONICS, which are crosslinked by hydrogen bonding and/or by atemperature change, as described in Steinleitner et al., Obstetrics &Gynecology, 77:48-52 (1991); and. Steinleitner et al., Fertility andSterility, 57:305-308 (1992).

Other materials which may be utilized include proteins such as fibrin,collagen and gelatin. Polymer mixtures also may be utilized. For examplea mixture of polyethylene oxide and polyacrylic acid which gels byhydrogen bonding upon mixing may be utilized. In one embodiment, amixture of a 5% w/w solution of polyacrylic acid with a 5% w/wpolyethylene oxide (polyethylene glycol, poloyoxyethylene) 100,000 canbe combined to form a gel over the course of time, e.g., as quickly aswithin a few seconds.

Covalently crosslinkable hydrogel precursors also are useful. Forexample, a water soluble polyamine, such as chitosan, can becross-linked with a water soluble diisothiocyanate, such as polyethyleneglycol diisothiocyanate. The isothiocyanates will react with the aminesto form a chemically crosslinked gel. Aldehyde reactions with amines,e.g., with polyethylene glycol dialdehyde also may be utilized. Ahydroxylated water soluble polymer also may be utilized.

Alternatively, polymers may be utilized which include substituents whichare crosslinked by a radical reaction upon contact with a radicalinitiator. For example, polymers including ethylenically unsaturatedgroups which can be photochemically crosslinked may be utilized, asdisclosed in WO 93/17669. In this embodiment, water soluble macromersthat include at least one water soluble region, a biodegradable region.and at least two free radical-polymerizable regions, are provided. Themacromers are polymerized by exposure of the polymerizable regions tofree radicals generated, for example, by photosensitive chemicals and orlight. Examples of these macromers are PEG-oligolactyl-acrylates,wherein the acrylate groups are polymerized using radical initiatingsystems, such as an eosin dye, or by brief exposure to ultraviolet orvisible light. Additionally, water soluble polymers which includecinnamoyl groups which may be photochemically crosslinked may beutilized, as disclosed in Matsuda et al., ASAID Trans.,38:154-157(1992).

Water soluble polymers with charged side groups may be crosslinked byreacting the polymer with an aqueous solution containing ions of theopposite charge, either cations if the polymer has acidic side groups oranions if the polymer has basic side groups. Examples of cations forcrosslinking of the polymers with acidic side groups to form a hydrogelare monovalent cations such as sodium, and multivalent cations such ascopper, calcium, aluminum, magnesium, strontium, barium, and tin, anddi-, tri- or tetra-functional organic cations such as alkylammoniumsalts. Aqueous solutions of the salts of these cations are added to thepolymers to form soft, highly swollen hydrogels and membranes. Thehigher the concentration of cation, or the higher the valence, thegreater the degree of cross-linking of the polymer. Additionally, thepolymers may be crosslinked enzymatically, e.g., fibrin with thrombin.

Other examples of fillers are hyaluronic acid, cellulose, alginate, andgelatin, which are available from commercial sources, e.g.,Sigma-Aldrich, Inc. and ICN Biomedicals, Inc. Hyaluronic acid is amaterial that is accepted in the medical community as a material thatmay be implanted into a patient; other commercial sources are GenzymeAdvanced Biomaterials (e.g., HyluMed®), LifeCore Biomedical, and FMCBioPolymer. Another example of a filler is cellulose, e.g., Avicel® athixotropic cellulose product from FMC BioPolymer. Another fillerexample is synthetic polymer hydrogels, e.g., as made by AngiotechPharmaceuticals, e.g., Coseal®. Other fillers are described in, e.g.,U.S. Pat. No. 6,224,893, and other references set forth herein.

Another embodiment is a filler that comprises a device having areversible volume, for example, a balloon. A balloon may be introduced,inflated, and then deflated after a dose of radiation has beenadministered, or recovered after the radiation treatment has beencompleted.

In use, a device for delivering a filler to a body may be loaded with afiller, and the filler introduced into the body, preferably so that thedistance between a first and a second tissue in the body is therebyincreased. A further step may include administering a dose of radiationto a tissue, preferably so that the second tissue receives lessradiation than it would have received if the distance between the firstand second tissue had not been increased. A further step may also beadministration of cryogenic treatment to the first or second tissue or atissue nearby. The radiation may alternatively be directed to a thirdtissue so that the first tissue or the second tissue received a loweramount of radiation as a result of its separation from the othertissue(s). The first tissue and the second tissue may be adjacent toeach other in the body, or may be separate from each other by othertissues. In many cases, such separation does not reduce the beneficialeffects of achieving separation between the first and second tissue.

Filler volumes for separating tissues are dependent on the configurationof the tissues to be treated and the tissues to be separated from eachother. In many cases, a volume of about 20 cubic centimeters (cc's ormls) is suitable. In other embodiments, as little as 1 cc might beneeded. Other volumes are in the range of 5-1000 cc, and all rangestherebetween, e.g., 5-400 cc, 10-30 cc, 15-25, cc, 10-150 cc, 20-200 cc,15-500 cc, 50-1000 cc, and 30-200 cc. In some embodiments, filers areadministered in two doses at different times so as to allow the tissuesto stretch and accommodate the filler and thereby receive a largervolumes of filler than would otherwise be readily possible.

An example of a delivery device is a syringe. The filler is loaded intothe syringe and injected through a needle into a body. Another exampleis a device that accepts, e.g., a folded, deswelled, or rolled fillerand provides a propelling mechanism to propel the filler through aneedle or catheter into a body. Propulsion may be by, e.g., a handle, aplunger, gas, or liquid force.

Another embodiment is a kit for introducing a filler into a body. Thekit may include a filler and a device for delivering the filler to thebody. The filler may be capable of undergoing a change in state afterits introduction into the body: for example, a collagen solution forms acollagen gel after entering the body, and a dehydrated sponge imbibeswater to increase its volume after exposure to physiological conditions.Embodiments include instructions for use. Embodiments includeanesthetics mixed with the filler or separate therefrom. Embodimentsinclude kits wherein the delivery device is a syringe, and otherembodiments include a needle for the syringe, and may include a needlefor administering the filler and/or the anesthetic.

Instructions may be included with a kit. Instructions may include wordsthat direct a user in a use of a kit. Instructions may be fully orpartially included with the kit, including as an insert, on a label, ona package, in a brochure, a seminar handout, a seminar display, aninternet teaching course, or on an internet or intranet web site. Forexample, a label on a kit could reference an internet address havinginstructions. Instructions may include explanations of embodiments setforth herein. Instructions may include dose histograms, and explanationsof suitable filler volumes for use.

Preferred anesthetics are local anesthetics, particularly 1% lidocainefor use in applying a filler to a body to displace the rectum from theprostate gland. The lidocaine may be used to perform a nerve block. Apreferred needle for anesthetic application is a short 22-gauge needleand a 7 cm 22-gauge spinal needle. A preferred needle for delivering afiller via syringe injection is an 8-gauge spinal needle that is 3.5 cmlength. Kist may include anesthetics.

EXAMPLE 1 Sample Protocol

This example describes a protocol for reducing the radiation exposure ofa tissue by increasing the distance between the tissue and a nearbytissue that is to be target for radioactive treatment. This example iscast in terms of using a space between the rectum and prostate, but anytwo tissues, or portions thereof, may be separated by following thisprotocol and introducing the filler between the tissues instead of intoDenovillier's space. Human collagen is used as the filler, but otherfillers may be substituted.

Protocol:

-   -   a) Inject human collagen into the space (Denovillier's space)        between the rectum and prostate.    -   b) Administer an effective volume of human collagen into        Denovillier's space to decrease the radiation dose to the rectum        during radiation therapy of the prostate, and change the rectal        dose volume histogram.    -   c) Assess the effectiveness of human collagen in lowering the        dose of radiation to the rectum during prostate radiation        therapy.    -   d) Evaluate the acute side effects of radiation during therapy        compared to historical controls.

Patient Eligibility:

-   -   a) Male with biopsy-proven prostate cancer.    -   b) Age:>18 years of age.    -   c) Elected conformal radiotherapy for cure or for palliation,        i.e., local control due to known metastases.    -   d) Suitable to undergo a transrectal ultrasound for        determination of space between rectum and prostate.    -   e) Suitable to receive a local anesthetic prior to receiving the        human collagen injection.    -   f) Tolerated a subcutaneous injection of human collagen to rule        out hypersensitivity to the collagen products.    -   g) Signed a study specific consent form.

Patient Contraindications:

-   -   a) Allergic to human collagen injection.    -   b) Does not tolerate human collagen injection for any reason.

Protocol Treatment—Methods and Materials

-   A. Prior to proceeding with the collagen injection, a diagnostic CT    scan of the pelvis or a planning CT scan of the pelvis will be    performed with the patient in the supine treatment position. Prior    to obtaining the planning CT scan, a Foley catheter will be inserted    into the bladder and drained. Fifty cc's of 50% diluted Conray will    be instilled into the bladder for visualization. The Foley catheter    will then be removed. Five cc's of 50% diluted Conray will be    injected into the penile urethra and retained with a penile clamp    for delineation. A rectal tube will be inserted into the rectal    vault. Thirty-five cc's of diluted contrast will be injected into    the rectal vault for delineation. The planning CT scan of the pelvis    will be obtained.

The outside surface of the prostate, bladder and rectum will becontoured (e.g., computer outlining of organs). The rectal contour willextend from the anal verge up to the rectosigmoid junction or to the topof seminal vesicles, whichever is greater, provided there is adequatepelvic parenchymal space so that minimal radiation dose is delivered tothe upper rectum.

A complex 3-D isodose treatment plan with a 3-D rectal dose volumehistogram (DVH) will be generated using a conformal six-field technique.Pre-injection and post-injection measurements will be determined betweenthe anterior rectal wall and the posterior border of the prostate.

-   B. Procedure to place the filler.

The patient will be placed in the dorsolithotomy position with both legsup in stirrups. The transrectal ultrasound probe will be placed withinthe rectal vault. A syringe with a 20-gauge needle will be used toadminister a local anesthetic. Preferably, a nerve block is performed tothe inferior branch of the pudendal nerve using a 7 cm 22-guage spinalneedle to adminsiter 5 cc of 1% lidocaine to the left and rightpara-vesicular region located just laterally of the seminal vesicles. Asecond syringe with a 16-gauge spinal needle will be inserted into theperineum and rotated to increase the potential space between the rectumand prostate. The same syringe will inject normal saline into the spacebetween the rectum and prostate to further increase the capacity of thispotential space.

Once the normal saline has been injected, a third syringe with a16-gauge spinal needle will be used to inject a 5-10 mm layer of humancollagen along the posterior wall of the prostate between the prostateand rectum. Once the collagen has been injected into the space betweenthe rectum and prostate, ultrasound images will be obtained to determinethe echogenicity of the collagen as well as to correlate the measuredultrasound volume to the CT obtained volume. All used syringes will bediscarded in a safe manner.

-   C. A second planning CT scan of the pelvis with simulation will be    performed after placement of the collagen injection using the same    technique. A 3-D computer generated isodose treatment plan will be    generated with a rectal DVH. Differences between the rectal DVH's    will be noted.-   D. The patient will than proceed with the conformal radiotherapy to    a dose of about 7560 cGy in 42 daily treatment fractions.-   E. During the course of treatment, the patient will be monitored for    changes in bowel frequency, symptoms of proctitis, and amount of    medications used if necessary.-   F. A third planning CT with simulation will be performed on the    first five patients after they have received 15-20 daily radiation    treatments. If there has been no significant reduction in collagen    volume nor significant changes in the rectal dose per the DVH, the    third planning CT scan will be discontinued.-   G. A fourth planning CT scan with simulation will be performed on    the last day of treatment. Again, a 3-D complex computer plan will    be generated to determine the rectal DVH. Measurements will be    compared to the previous DVH's. If there has been no significant    reduction or change in collagen volume nor significant changes in    the rectal dose per the DVH, the fourth planning CT will be    discontinued after 20 patients.-   H. A fifth planning CT scan with simulation and simulation for    dosimetric purposes will be performed approximately 4-6 months after    completion of the radiation therapy or 6-8 months after the    injection of collagen into the space between the rectum and    prostate. This scan will be performed for the first five patients    and than discontinued.    Treatment Evaluation:

The results will provide the following information:

-   -   Toleration of injection of human collagen into the space between        the rectum and prostate.    -   Extent of anterior displacement of prostate from injection of        human collagen.    -   Amount of radiation dose delivered to anterior wall of rectum.    -   Amount of dose reduction to rectum per dose volume histogram        (DVH).    -   Clinical changes of bowel habits and treatment intervention        during the course of radiation treatments, if any.        Descriptive Factors:    -   Relationship of cc's of human collagen to forward displacement        of prostate.    -   Description of homogeneous distribution of human collagen        between rectum and prostate as determined per ultrasound and CT        scan.    -   Relationship of cc's of human collagen to change of rectal dose        volume histogram.        Nursing Evaluation and Treatment Follow-up:

A weekly assessment of patients will include a review of tolerance oftreatment, bowel habit changes and treatment interventions. Typically,medical interventions can include but are not limited toanti-hemorroidal creams/ointments, anti-diarrhea medications,anti-spasmodic medications, alpha-1 inhibitors and analgesics with orwithout narcotics.

Patient review will be conducted at 2 weeks, 1 month, 3 months and 6months after completion of radiation therapy. The patient will than befollowed on a routine serial basis that is recommended for all cancerpatients after receiving radiation therapy.

Consistency Normal = N Incontinence Number Soft = S Anti- Anti- of Urine(U) of BM's Hard = H Anal diarrhea Hemorrhoid or per day Loose = 1Discomfort Medication Medication Stool (S) Consultation Day 1 of XRT Wk1 Wk 2 Wk 3 Wk 4 Wk 5 Wk 6 Wk 7 Wk 8 2 Weeks 1 Month 3 Months 6 Months 1Year 1.5 Years 2 Years 2.5 Years 3 YearsHuman Collagen:

Human collagen is commercially available from multiple manufacturers.Human collagen has been FDA approved to be injected into patients and inparticular the pelvis and perineurium of humans. The FDA has alsoapproved the use of human collagen during radiation brachytherapy.Brachytherapy will deliver a dose that is believed to be immeasurable atthe surface of the radioactive isotope but can range from 300-600 Gy orgreater. The traditional radiation dose delivered to the prostate rangesfrom 70-76 Gy. However, modern technology using 3-D conformal radiationor Intensity Modulated Radiotherapy (IMRT) has allowed dose escalationupwards to 100 Gy. These doses are well below the dose of 145 Gy usedfor brachytherapy or the surface dose of a radioactive isotope.

Human collagen is typically commercially supplied in preloaded syringescontaining 5 or 10 cc's of collagen. The unit is sterile and comessealed. The pack will be stored and inspected for damage prior to beingopened. If one suspects a damaged product, it will not be used. Thehuman collagen will be removed from its package only prior to undergoingthe injection procedure as previously outlined.

Protocol. A syringe with an anesthetic will be used to obtain localanesthesia. A second needle will be inserted into the perineum betweenthe potential space between the rectum and prostate. This needle will berotated to further open the space between the rectum and prostate(Denovillier's space), and normal saline will then be injected tofurther increase this potential space. The human collagen will then beinjected into this space using ultrasound guidance.

Once the human collagen has been injected into the perineum as desired,the used syringes will be discarded in a safe manner.

EXAMPLE 2 Treatment of Ten Males

This protocol involved injecting an effective volume of human collageninto Denovillier's space to displace the rectum away from prostate. Aconventional computer plan used for radiation treatment planning wasused to determine the reduction of dose to the rectum (dose volumehistogram) corresponding to the collagen injection. Accordingly,patients were monitored during their 2 months of radiation treatments toassess acute radiation induced side effects.

Ten men with stage 1 or stage 2 prostate cancer were informed of theongoing procedure and elected to participate.

Prior to the collagen injection, each patient underwent a CT simulationto obtain CT images to be used for a radiation computer intensitymodulated radiotherapy (IMRT) treatment plan without human collagen. Allmen received their human collagen injection from the same urologist asan outpatient. To perform the injection, each man was placed in the leftlateral decubitis position. An ultrasound transducer was positioned intothe rectum so that the entire prostate was well visualized. A 7 inch 22gauge spinal needle was used to perform a bilateral pudendal nerve blockusing 2% lidocaine. After obtaining adequate anesthetic effect, a 5.5inch 18 gauge spinal needle was positioned into the space between therectum and prostate using ultrasound guidance. Once the needle locationwas believed to be within Denovillier's space, 5-10 cc's of normalsaline was injected to open the potential space between the rectum andprostate. Real time ultrasound guidance was used to confirm that theneedle was anterior to the rectal wall and posterior to the prostate andtherefore within Denovillier's space. This process is depicted in FIGS.1-3, with patient 100 having space 102 between rectum 104 and prostate106 receiving needle 108 into space 102, with needle 108 being incommunication with syringe 110 that contains collagen filler 112. Thesyringe plunger is depressed to introduce collagen filler 112 into space102.

Once it was confirmed that the normal saline was within Denovillier'sspace, the protocol proceeded to the injection of human collagen usingthe same 5.5 inch gauge 18 spinal needle. Each of the 10 men who enteredinto the protocol received 20 cc's of human collagen. Their prostatevolumes ranged from 35 cc up to 90 cc's.

Following placement of 20 cc's of human collagen, the needle was removedand then the ultrasound transducer. Approximately, 5 days following thecollagen injection each man underwent a second CT simulation to obtain asecond IMRT radiation computer treatment plan with the collageninjection. Five days were provided to allow reabsorption of the normalsaline and the human collagen to “settle” within Denovillier's space.

FIG. 4 depicts a CT scan of a man that received a collagen filler. Theman 200 received about 20 cc of collagen filler into the space 212between rectum 204 and prostate 206. The space 204 is enlarged so thatthe radiation exposure of rectum 204 is reduced.

The first and second IMRT radiation computer treatment plans werecompared to evaluate the displacing properties of human collagen andassess the reduction in radiation dose to the rectum. A third IMRTradiation computer treatment plan was obtained on the last day oftreatment to confirm that there had been minimal change throughout theirtreatment.

During the 2 months of external beam radiation, each person wasinterviewed on a weekly basis. Quality of life issues were assessedregarding their urinary and bowel habits.

CT scans were obtained 6 months and 12 months following completion oftheir radiotherapy to monitor absorption of human collagen.

Results: Each man who elected to proceed with the ongoing protocoltolerated the collagen injection very well. No one reported symptomssuggestive of an allergic reaction. Three men reported a sensationsimilar to a light rectal pressure that resolved 3-4 hours after theinjection. One man experienced urinary retention and required placementof a Foley catheter. The catheter was removed 3 days after the injectionwithout difficulty or recurrence. It is believed that the urinaryretention was secondary to the pudendal nerve block.

All men received prostate treatment to a dose of 75.6 Gy in 42fractions. Their treatment was delivered using an IMRT 6-fieldtechnique. Conventionally, a highly positive outcome is if 30% of therectum receives 45 Gy or less and 10-15% receives 60 Gy or more.

All of the patients had 20-25% of the rectum receiving 45 Gy or lessprior to the collagen injection. Following the collagen injection, 7-15%or the rectum received 45 Gy or less. Moreover, <5% of the rectumreceived a dose of 60 Gy or more.

All men who received a collagen injection prior to their radiationtreatments experienced no change in their bowel habits. Interestingly,one man underwent an unplanned flexible sigmoidoscopy 6 months aftercompleting his radiotherapy. His physician who performed thesigmoidoscopy reported an entirely normal exam without any evidence ofradiation treatments.

Five of the 10 men experienced urinary frequency, diminished urinaryflow and urgency. Four men elected to be treated with an alpha 1 blocker(Flomax) with success.

The invention has been described in language more or less specific as tostructural and methodical features and by reference to detailed examplesand methodologies. It is to be understood, however, that the inventionis not limited to the specific features shown and described, since themeans herein disclosed comprise preferred forms of putting the inventioninto effect, and the examples are not meant to limit the scope of theinvention. It should be understood that variations and modifications maybe made while remaining within the spirit and scope of the invention,and the invention is not to be construed as limited to the specificembodiments described or as shown in the drawings. All patents, patentapplications, journal references, and publications referenced herein arehereby incorporated by reference herein.

1. A method of delivering a therapeutic dose of radiation to a patientcomprising introducing a biocompatible, biodegradable filler devicebetween a first tissue location and a second tissue location to increasea distance between the first tissue location and the second tissuelocation, and treating the second tissue location with the therapeuticdose of radiation so that the presence of the filler device causes thefirst tissue location to receive less of the dose of radioactivitycompared to the amount of the dose of radioactivity the first tissuelocation would receive in the absence of the filler device, wherein thefiller device is introduced an injectable material and is a gel in thepatient that is removed by biodegradation of the filler device in thepatient wherein the first tissue location is associated with the rectumand the second tissue location is associated with the prostate gland. 2.The method of claim 1 wherein the filler is introduced intoDenovillier's space.
 3. The method of claim 1 wherein the fillercomprises a member of the group consisting of alginate, gelatin, fibrin,fibrinogen, albumin, polyethylene glycol, thixotropic polymers,thermoreversible polymers, and mixtures thereof.
 4. The method of claim1 wherein the filler comprises at least one therapeutic agent.
 5. Themethod of claim 4 wherein the at least one therapeutic agent is a memberof the group consisting of an anti-inflammatory drug, an antibiotic, anantimycotics, a hemostat, a steroid, and an analgesic.
 6. The method ofclaim 1 wherein the filler is biodegradable in vivo in less thanapproximately 90 days.
 7. The method of claim 1 wherein the fillercomprises an extracellular matrix molecule.
 8. The method of claim 1wherein the filler consists essentially of collagen.
 9. The method ofclaim 1 wherein the filler comprises at least one polysaccharide. 10.The method of claim 9 wherein the at least one polysaccharide ishyaluronic acid.
 11. The method of claim 1 wherein the filler furthercomprises a member of the group consisting of a degradation inhibitor, aradio opaque marker, and an osmotic agent that causes water to becomeassociated with the filler material by osmosis.
 12. The method of claim1 wherein the filler further comprises a buffering agent.
 13. The methodof claim 1 wherein the filler comprises a member of the group consistingof a degradation inhibitor, a radio opaque marker, and an osmotic agentthat causes water to become associated with the filler material byosmosis.
 14. The method of claim 1 wherein the filler comprises abuffering agent.
 15. The method of claim 1 wherein the filler materialcomprises a synthetic polymer.
 16. The method of claim 1 wherein thefiller occupies a volume in the range of about 10 to about 200 cubiccentimeters in a patient.
 17. A method of delivering a therapeutic doseof radiation to a patient comprising: (i) injecting anesthesia and (ii)injecting saline to expand the space between the first and second tissuelocation, wherein the first tissue location is associated with therectum and the second tissue location is associated with the prostategland and introducing a biocompatible, biodegradable filler devicebetween the first tissue location and the second tissue location toincrease a distance between the first tissue location and the secondtissue location, said biocompatible, biodegradable filler being collagenand introducing collagen into Denovillier's space and treating thesecond tissue location with a therapeutic dose of radiation, saidtherapeutic dose of radiation being 70 to 100 Gy, so that the presenceof the filler device causes the first tissue location to receive lessthan 50% of the dose of radioactivity compared to the amount of the doseof radioactivity the first tissue location would have received in theabsence of the filler device, wherein the filler device is removed bybiodegradation of the filler device in the patient.
 18. The method ofclaim 1 wherein the filler comprises a member of the group consisting ofpolylactide, polyglycolide, polycaprolactone, poly(alpha-hydroxy acid).19. The method of claim 1 wherein the filler comprises alginate.
 20. Themethod of claim 1 wherein the filler comprises gelatin.
 21. The methodof claim 1 wherein the filler comprises fibrin or fibrinogen.
 22. Themethod of claim 1 wherein the filler comprises albumin.
 23. The methodof claim 1 wherein the filler comprises polyethylene glycol.
 24. Themethod of claim 1 wherein the filler comprises a thixotropic polymer.25. The method of claim 1 wherein the filler comprises athermoreversible polymer.